All the prior arts describe systems for verification of currency notes claiming that the systems can be applied for other security documents also. Accordingly, in the following analysis of prior arts the word currency note is used rather than generic term security document. Presently available currency detectors can be classified into two categories, namely viewer type and automated type. All the viewer type instruments rely on subjective visual assessment of authenticity. Few of the viewers display a magnified view of micro-features under visible light. In some the viewers, a currency note is illuminated by UV light to display fluorescent security features like fibres, UV fluorescent printed pattern. Most automatic type detection systems are currency counters also. The verification in some automated type systems is based on UV measurement of fluoresced/reflected UV radiation from a narrow strip of the currency note; the data are collected by moving the note across a detector and measuring the energy from a small area at a time i.e. by scanning and sampling technique. The measured energy is converted into an electrical signal. Data acquired from a genuine currency notes is set as reference. Any deviation of the measured signal from this reference value is indicative of counterfeit. The few of the automatic verifiers measure reflected/fluoresced UV light from UV fluorescent security feature(s). Some currency verifiers are based on scanning a part of the printed pattern and looks for inconsistent locations of the small dots of the printing material. With the advent of technology, art of counterfeiting is also progressing rapidly. Earlier, fake currencies were produced either by colour scanning followed by high-resolution printing (alternatively colour photocopying) or by crude printing on non-security papers. The today's bank notes incorporate several security features like intaglio printing, optically variable ink (OVI) features, and UV fluorescent features including fluorescent fibres. Clever counterfeiters are now attempting to duplicate these features including fluorescent properties of the paper. A very thin line of demarcation now exits between a counterfeit currency note and an authentic one. At least two different modes of verification are imperative to assess the authenticity. The visual and UV fluorescent security features incorporated in a currency note vary from country to country and also denomination dependent. The judgement of authenticity of a currency note relying either on visual assessment or on rapid opto-electronic detection ‘on-the-fly’ technique based on scanning the light reflected or transmitted from a narrow zone may likely to yield misleading conclusions. A suitable apparatus providing the combination of integrated reflected as well as transmitted energy, received from a large area of a currency note, measurement facilities in at least three different wavebands both for the reflected and transmitted components, in static condition of the currency note, which can be adopted for the currencies from various countries of different denominations or in various physical conditions of the note to be inspected is not available.
Analysis of Prior Art
The following basic principles are used to verify the genuineness of a currency note:                i Visually observing the UV fluorescent features, printed or embedded, of the currency note        ii Reading the magnetically recorded code by a magnetic sensor        iii Assessing the quality of print by studying the mis-registration        iv Assessing the currency paper quality by measuring the quantum of UV light reflected/transmitted        v Assessing the currency paper quality by measuring the quantum of UV light fluoresced        vi Assessing a electronically recorded image        vii Multifunctional apparatus for discrimination and authentication        
All the above cited prior arts rely on one of these principles—variations are in the techniques of data collection and the area of the currency note from where data are collected. The drawbacks of the prior arts are discussed below.
The paper used in currency notes has cotton based fibres as the base material that shows very little UV fluorescent property. Other types of paper convert incident UV radiation into visible light. The amount of UV light reflected and fluoresced are complimentary as higher is the quotient of fluorescence, less is the amount reflected and vice versa. So, the measurement one or the other provides similar information. Transmittance also depends on fluorescence since, if large fluorescence will reduce the transmitted components. Accordingly, principles mentioned under (iii) and (iv) above are some similar in nature, data interpretations. All the existing prior arts employing the principals (ii) and (iii) differ in the measurand, and technique of scanning and the zone of data acquisition. These have common limitations. The drawbacks of the all the prior arts are discussed below, apparatuses are classified in accordance with their principle of operation.
Visually Observing the Printed or Embedded UV Fluorescent Features
Prior arts listed in the U.S. Pat. No. 5,942,759 and US2001054644 belongs to this category. These are basically viewers where in the operator exposes the currency note to UV radiation and looks for the presence or absence of printed or embedded UV fluorescent features like serial no., floral or other patterns, thread and fibres etc. These instruments rely on two dimensional image capabilities of human eye and data processing power of the brain. Drawbacks are:                Decision is subjective and needs a priori knowledge about an authentic currency note identical in all respect, except physical conditions, to the one under verification.        It is practically impossible to stock standard samples either as images in the brain or physically corresponding currency notes of different denominations from various countries.        
Modern counterfeits incorporate many UV fluorescent printed features to fool an operator relying on visual inspection only. Viewer types are not relevant to the present invention.
Magnetic Sensor Based Equipment
Prior arts listed in the U.S. Pat. No. 4,464,787 and U.S. Pat. No. 5,874,742 fall under this category. The drawbacks are:                Magnetic code readers are basically currency discriminators—magnetic code can be duplicated easily and hence not a reliable method of authentication        Currency notes from many countries do not contain magnetic codes. Genuineness of currency notes from these countries can not be assessed.        Magnetic code of a currency note may be wiped out due to accidental exposure to strong magnetic field, magnetic sensor based instruments would fail to authenticate such a note.        Some machines scan the currency note to determine its dimensions for hence authentication. Dimensional data is unreliable.        
These apparatuses are also not closest prior art.
Instruments Based on Assessing the Quality of Print by Studying the Mis-Registration
Prior arts listed in the U.S. Pat. No. 4,482,971 belong to this category. Currency notes counterfeited by high resolution scanning and printing or colour photocopying process. The instruments scan and look for presence of small dots of printing ink inconsistent with the printed pattern. The main drawback is:                Modern counterfeited currency notes are printed in sophisticated notes duplicating most of the processes employed to print authentic currency notes without any discernable mis-registration error. These types of notes cannot be authenticated by studying the mis-registration error.        
These apparatuses are also not closest prior art.
Instruments Based on of the Quantum of UV Light Fluoresced/Reflected/Transmitted Energy Measurement
Prior arts listed in the U.S. Pat. No. 4,482,971 and FR2710998 belongs to this category. All of these scan a narrow zone, sampling a small area at a time, while the currency note moves below or over the photodetector. Measurand is either the reflected or transmitted or fluoresced component of incident UV light (there is only one patent, FR2710998, which measures transmitted energy and the rest measure the reflected energy). UV light is either blocked (fluorescent measurement) or rest of the optical spectrum is blocked only UV light is allowed to pass (UV reflectance/transmittance measurement) by a filter. The drawbacks are:                Measured fluoresced/reflected/transmitted energy data corresponding to UV region of the spectrum alone cannot reliably characterize the paper quality. Cleverly counterfeited currency notes can mimic UV fluoresce/reflection/transmission coefficient sufficiently close to that of a currency paper.        The source is kept very close to the moving currency note, so the data are collected from a very small area. The measured energy from each small sampled area is either compared to a reference data (collected from similar type authentic currency note) or summed up to compare with similar data collected from a reference sample. Soiling and or mutilations of the currency under authentication would cause substantial amount of data distortion to reliably assess authentication.        It is known that an accidentally washed genuine note in certain detergent develops UV fluorescent quality. Such a note would be indicated as a counterfeit.        This principle needs motion of the currency note, and performs only first order verification during stacking/counting of unsoiled notes of similar type. It is not a compact and cheap system.        Some apparatuses measure the fluorescent energy emanated from certain printed features, e.g. thread. These need accurate placement of the said feature(s) under the photodetector. Since currency notes of different denominations from different countries contain UV sensitive features at different locations, instruments based on measuring UV fluorescence (by any printed pattern) can be usefully employed for US Dollars only, as all US Dollars have same size and are reasonably similar.        
There is only one U.S. Pat. No. 4,618,257 which uses multiple sources emitting different waveband to illuminate a very small zone of the currency note under verification and a single detector collects the energy for each waveband in sequential manner. Since the data corresponds to a small zone, local physical condition, like soiling, mutilation etc. would severely affect the proper authentication process.
Assessing a Electronically Recorded Image
The patent US20030169415 uses a CCD camera to record the image and by tri-chromatic colour analysis technique judges the authenticity. The drawbacks are:
Soiling, mutilation, physical damage etc. would lead to erroneous results
Expensive and complex
Basically designed for passport and similar kinds of documents.
Multifunctional Apparatus for Discrimination and Authentication
US20030081824A1, claims for an improved fake currency detector using different kinds of sensor output. A brief description of is principle of operation and drawbacks are given below:
A multifunctional apparatus is using multiple magnetic and optical sensors. The magnetic sensors scan and generate a magnetic code. Optical sensors scan the currency note in terms reflected energy in two wave bands. Colour matching scheme is also has been claimed to be employed. The two types filters used are used, namely UV pass and UV blocking. UV blocking visible pass filter is made a combination of two filters namely a blue filter passing 320 nm to 620 nm with a peak at 450 nm and a yellow filter passing 415 to 2800 nm. So, the visible light sensor sees 415 nm to 620 nm i.e. it senses blue to a small part of red colour.
The drawbacks are:                Authentication is largely dependent on magnetic and optical scanning. Currency notes of many countries do not have any magnetic code.        In many countries, old notes have threads which do not contain any special optical feature. Such notes would be identified as fake, even if genuine.        The optical authentication is based on thread parameters. Currency notes of many countries, including India, have different series of same denomination with a wide variation in thread locations. The tolerance limit of 0.05 inch permissible in the patent application would reject authentic currency notes.        A genuine note accidentally discoloured due to bleaching etc. would be indicated as fake.        The principle used can not properly authenticate genuine currency notes having no fluorescence feature (text or thread), such as Asoka pillar Indian currency series of Rs.50 and Rs.100 denomination notes, still in wide circulation in India.        The optical authentication is based on printed image pattern and thread data. Clever counterfeiter can duplicate printed patterns.        The apparatus can not detect NIR sensitive features likely to incorporate in the currency notes of various countries.        The apparatus is complex, expensive and not portable.        
Another prior art U.S. Pat. No. 4,618,257 incorporates two LEDs positioned at such angles that they illuminate a common target area and a broad band photo detector to measure the light reflected from the target area. As the currency note is transported under the LEDs, each of the LEDs is switched on sequentially with a pre-determined ‘on-time’ and ‘delay time’. The preferred LED pair is comprised of one narrow band red LED and the other narrow band green LED having peak emission wavelengths of 630 nm and 560 nm respectively. The patent suggests the alternative use of yellow or infrared LED. The measured signals in terms of voltages are compared with the corresponding reference values stored in a memory. The drawbacks of this apparatus are:                It does not collect any data corresponding to the reflectance or fluorescence of UV or blue colour. Reflectance information is confined to only about half of the optical spectral range of 350 to 750 nm. Our experiment has shown, as explained later in Example 1, that UV-blue reflectance property of a currency note is a strong indicator of its genuineness due to the very basic nature of the currency paper.        Due to various reasons including local conditions of a currency note, reflected data from a small area may not be the true representative of the bulk properties.        The apparatus collects data from a specified small target area making it highly position sensitive particularly in case of currency notes of varied sizes.        
All known automated currency verifiers require transport mechanism, and cannot operate in stationary condition of the document under verification. These verifiers pick up one document from a stack of multiple number of similar documents, transport it from one place to other and verify authenticity on the fly by scanning it. Such systems are suitable basically for currency note with a number of currency notes stacked in a pile, but can not properly handle one off a kind documents like bank draft, security bond and other bank instruments where each document is likely very different from the other in shape, size and other similar parameters. There is no patent sealed or filed till date wherein one off a kind documents like, bank drafts, security bonds and other bank instruments and security documents which require manual feeding can be authenticated by a unique automatic detection mode.
There is no patent sealed or filed till date, which embodies automatic opto-electronic detection techniques using at least three optical wavebands to generate reflectance/fluorescence data by measuring reflected/fluoresced energy together with a provision visual inspection under UV-visible-near infra red light.
There is no patent sealed or filed till date, which embodies automatic opto-electronic detection technique using more than one optical wavebands to obtain reflectance/fluorescence data by spatially integrating energy received from a large area of the document under verification.
There is no known prior art claiming to authenticate polymer based currency notes, passport, visa, various bank instruments visually as well as automatically.
The present invention circumvents the drawbacks of existing prior arts by providing two independent methods of verification and more than one optical band to detect authenticity in automatic mode in a stationary condition of the document under authentication by performing large area spatial and temporal integrations simultaneously. However, the automatic detection module of the invention can be adopted in a currency note counting machine by collecting dynamic data at various scanning points. The present invention provides an apparatus that can be used to authenticate paper and polymer based currency note, bank drafts, security bonds and other bank instruments and security documents without any need to modify system hardware.